Parent device allocation of retransmit slot to child network device on behalf of peer child device in a deterministic network

ABSTRACT

In one embodiment, a method comprises receiving, by a parent network device in a wireless deterministic network, a retransmit capabilities message from a first child device attached to the parent network device, the retransmit capabilities message specifying that the first child device can detect a data packet transmission to the parent network device by a second child device attached to the parent network device and that is a peer of the first child device; and allocating, by the parent network device, a peer retransmit timeslot to the first child device from within a channel distribution chunk appropriated by the parent network device, the peer retransmit timeslot enabling the first child device to retransmit a data packet on behalf of the second child device to the parent network device.

TECHNICAL FIELD

The present disclosure generally relates to a parent network deviceallocating a retransmit slot to a child network device on behalf of apeer child device in a deterministic network, for example an IPv6 TimeSlotted Channel Hopping (6TiSCH) based network.

BACKGROUND

This section describes approaches that could be employed, but are notnecessarily approaches that have been previously conceived or employed.Hence, unless explicitly specified otherwise, any approaches describedin this section are not prior art to the claims in this application, andany approaches described in this section are not admitted to be priorart by inclusion in this section.

The Internet Engineering Task Force (IETF) is attempting to proposestandards that can be applied to wireless devices for the stringentrequirements of deterministic networks (e.g., minimal jitter, lowlatency, minimal packet loss). For example, Low power and Lossy Networks(LLNs) allow a large number (e.g., tens of thousands) ofresource-constrained devices to be interconnected to form a wirelessmesh network. The IETF has proposed a routing protocol (“6TiSCH”) thatprovides IPv6 routing using time slotted channel hopping (TSCH) based onIEEE 802.15.4e, enabling LLN devices to use low-power operation andchannel hopping for higher reliability. Routes can be based on therouting protocol for LLNs (RPL).

The 6TiSCH architecture specifies a Channel distribution/usage (CDU)matrix of “cells”, each cell representing a unique wireless channel at aunique timeslot. The CDU is partitioned into prescribed “chunks”, eachchunk comprising multiple cells distributed in time and frequency (i.e.,a different channel each timeslot). The 6TiSCH architecture specifiesthat a RPL parent device can allocate cells within an appropriated chunkto its first-hop child devices within its interference domain.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the attached drawings, wherein elements having thesame reference numeral designations represent like elements throughoutand wherein:

FIG. 1 illustrates an example deterministic network having a parentnetwork device for allocating one or more retransmit timeslots to achild network device for retransmission on behalf of a transmittingdevice, for example a peer child device or the parent network device,according to an example embodiment.

FIG. 2 is a diagram illustrating retransmit timeslots allocated to achild network device from a slotframe of a channel distribution chunkappropriated by the parent network device of FIG. 1, according to anexample embodiment.

FIG. 3 illustrates an example implementation of any one of the networkdevices of FIG. 1, according to an example embodiment.

FIG. 4 illustrates an example method of allocating one or moreretransmit timeslots to a child network device on behalf of anothertransmitting device, according to an example embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a method comprises receiving, by a parent networkdevice in a wireless deterministic network, a retransmit capabilitiesmessage from a first child device attached to the parent network device,the retransmit capabilities message specifying that the first childdevice can detect a data packet transmission to the parent networkdevice by a second child device attached to the parent network deviceand that is a peer of the first child device; and allocating, by theparent network device, a peer retransmit timeslot to the first childdevice from within a channel distribution chunk appropriated by theparent network device, the peer retransmit timeslot enabling the firstchild device to retransmit a data packet on behalf of the second childdevice to the parent network device.

In another embodiment, an apparatus comprises a device interface circuitand a processor circuit. The device interface circuit is configured forreceiving, in a wireless deterministic network, a retransmitcapabilities message from a first child device attached to theapparatus, the retransmit capabilities message specifying that the firstchild device can detect a data packet transmission to the apparatus by asecond child device attached to the apparatus and that is a peer of thefirst child device. The processor circuit is configured for allocating apeer retransmit timeslot to the first child device from within a channeldistribution chunk appropriated by the apparatus. The peer retransmittimeslot enables the first child device to retransmit a data packet onbehalf of the second child device to the apparatus.

In another embodiment, one or more non-transitory tangible media areencoded with logic for execution by a machine and when executed by themachine operable for: receiving, by a parent network device in awireless deterministic network, a retransmit capabilities message from afirst child device attached to the parent network device, the retransmitcapabilities message specifying that the first child device can detect adata packet transmission to the parent network device by a second childdevice attached to the parent network device and that is a peer of thefirst child device; and allocating, by the parent network device, a peerretransmit timeslot to the first child device from within a channeldistribution chunk appropriated by the parent network device, the peerretransmit timeslot enabling the first child device to retransmit a datapacket on behalf of the second child device to the parent networkdevice.

In yet another embodiment, a method comprises sending, by a childnetwork device attached to a parent network device in a wirelessdeterministic network, a retransmit capabilities message to the parentnetwork device, the retransmit capabilities message specifying that thechild network device can detect a data packet transmission to the parentnetwork device by a second child device attached to the parent networkdevice and that is a peer of the child network device; and receiving, bythe child network device from the parent network device, a peerretransmit timeslot allocated to the child network device from within achannel distribution chunk appropriated by the parent network device,the peer retransmit timeslot enabling the child device to retransmit adata packet on behalf of the second child device to the parent networkdevice.

In another embodiment, an apparatus comprises a processor circuit and adevice interface circuit. The processor circuit is configured forgenerating a retransmit capabilities message for a parent network devicein a wireless deterministic network, the apparatus attached as a childnetwork device to the parent network device. The retransmit capabilitiesmessage specifies that the apparatus can detect a data packettransmission to the parent network device by a second child deviceattached to the parent network device and that is a peer of theapparatus. The device interface circuit is configured for sending theretransmit capabilities message to the parent network device. The deviceinterface circuit further is configured for receiving, from the parentnetwork device, a peer retransmit timeslot allocated to the apparatusfrom within a channel distribution chunk appropriated by the parentnetwork device. The peer retransmit timeslot enables the apparatus toretransmit a data packet on behalf of the second child device to theparent network device.

In another embodiment, one or more non-transitory tangible media areencoded with logic for execution by a machine and when executed by themachine operable for: sending, by a child network device attached to aparent network device in a wireless deterministic network, a retransmitcapabilities message to the parent network device, the retransmitcapabilities message specifying that the child network device can detecta data packet transmission to the parent network device by a secondchild device attached to the parent network device and that is a peer ofthe child network device; and receiving, by the child network devicefrom the parent network device, a peer retransmit timeslot allocated tothe child network device from within a channel distribution chunkappropriated by the parent network device, the peer retransmit timeslotenabling the child device to retransmit a data packet on behalf of thesecond child device to the parent network device.

DETAILED DESCRIPTION

Particular embodiments provide a scalable improvement in packet deliveryrates in deterministic data networks, based on introducing spatialdiversity using one or more child network devices (i.e., “childdevices”) that promiscuously detect data packet communications between apeer child device and a parent network device. The parent network devicein a tree-based network (e.g. a RPL network) can allocate one or moreretransmit timeslots to one or more child network devices attached tothe parent network device that can be used to retransmit data packets onbehalf of other network devices. The one or more retransmit timeslotscan be allocated by the parent network device from within a channeldistribution chunk appropriated by the parent network device within thetree-based network.

In response to the one or more child nodes determining an absence of anacknowledgement for a promiscuously-detected data packet during anidentifiable timeslot of the channel distribution chunk, a child nodecan retransmit the data packet, on behalf of the source of the datapacket, during the retransmit timeslot allocated by the parent networkdevice. If the first retransmission of the data packet is notacknowledged, a second child node can retransmit the data packet duringthe corresponding retransmit timeslot allocated to the second childnode. The original “source” of the data packet can be a “failing”transmitting child network device sending the data packet to the parentnetwork device and failing to receive an acknowledgement; the original“source” of the data packet also can be the parent network devicesending the data packet to a “failing” receiving child network devicethat fails to send an acknowledgement.

Hence, the example embodiments enable one or more of the child networkdevices directly attached to the parent network device to form a “bandof brothers” that can retransmit a data packet using an allocatedretransmit timeslot on behalf of a “failing” transmitting child networkdevice to the parent network device, or that can retransmit a datapacket on behalf of the parent network device to a “failing” receivingchild network device that fails to receive the data packet from theparent.

The example embodiments provide scalable spatial diversity based on theparent network device allocating each retransmit slot to a correspondingchild network device within the channel distribution chunk appropriatedby the parent network device; since the parent network device canappropriate (i.e., acquire or claim) the channel distribution chunkrelative to neighboring network devices within an interference domain,the retransmit slots allocated by the parent network device canguarantee retransmit opportunities without introducing any interferenceto neighboring network devices. Further, unnecessary retransmissions areavoided, since a child network device does not retransmit a data packetunless it determines an absence of a corresponding acknowledgementduring the timeslot allocated for the initial transmission of the datapacket.

FIG. 1 is a diagram illustrating an example network 10 having a parentnetwork device “N1” 12 and child network devices “N2” and “N3” 14 forretransmission of data packets, according to an example embodiment. Eachnetwork device 12, 14 is a physical machine (i.e., a hardware device)configured for implementing network communications with other physicalmachines via the network 10. The term “configured for” or “configuredto” as used herein with respect to a specified operation refers to adevice and/or machine that is physically constructed and arranged toperform the specified operation. Hence, each apparatus 12, 14 is anetwork-enabled machine implementing network communications via thenetwork 10.

The network 10 can be a stand-alone deterministic network, or can bepart of a larger deterministic data network having multiple networkdevices (e.g., constrained “Internet of Things” (IoT) network devices)arranged in a tree-based topology, for example a RPL based networkaccording to the Internet Engineering Task Force (IETF) Request forComments (RFC) 6550, that can build a destination oriented directedacyclic graph (DODAG) from multiple network devices having one or morepaths to a destination. As described below, each of the network devicescan organize themselves into a DODAG over a channel distribution/usage(CDU) matrix 16 according to 6TiSCH. Hence, the network 10 of FIG. 1 canillustrate a subsection of a directed acyclic graph (DAG), also known asa “sub-DAG”, where the parent network device “N1” 12 is a child networkdevice of another parent network device in another sub-DAG, and eachchild network device 14 can be a corresponding parent network device ofa corresponding sub-DAG.

FIG. 1 also illustrates that the parent network device “N1” 12, as partof organizing a DODAG over a CDU matrix 16, can appropriate (i.e.,acquire or claim) an unused one of the channel distribution chunks “H”18 relative to neighboring network devices (not shown) within aninterference domain. As illustrated in FIGS. 1 and 2, the CDU matrix 16according to 6TiSCH can include cells (e.g., “Cij”) 20, each cell “Cij”20 representing a corresponding timeslot “j” at a corresponding channelfrequency “i”. Hence, each channel distribution chunk 18 is based on aprescribed sequence 22 of cells 20, referred to in FIG. 2 as a slotframe22. As illustrated in FIGS. 1 and 2, the CDU matrix 16 can include thechannel distribution chunks “A”, “B”, “C”, “D”, “E”, “F”, “G”, “H”, “I”,and “J” 18. Other channel distribution chunks 18 may be present in thechannel distribution chunk 18. Hence, since each channel distributionchunk 18 can provide orthogonal frequency and time diversity relative toany other channel distribution chunk 18, each parent network device in aDODAG can appropriate for itself an unused channel distribution chunk 18relative to neighboring network devices within an interference domain(i.e., an overlapping wireless transmission area).

As illustrated in FIGS. 1 and 2, the channel distribution chunk “H” 18appropriated by the parent network device “N1” 12 is based on the “H”slotframe 22 including the sequence of cell “C81” 20 at slot time “HS1”24 (identifying the slot time “S1” for channel distribution chunk “H”),cell “C23” 20 at slot time “HS2” 24, cell “C44” 20 at slot time “HS3”24, cell “C65” 20 at slot time “HS4” 24, cell “C86” 20 at slot time“HS5” 24, cell “C28” 20 at slot time “HS6” 24, cell “C49” 20 at slottime “HS7” 24, etc.

The parent network device “N1” 12 can allocate transmit timeslots 26from the available slot times 24, resulting in a schedule 28 a for theparent network device “N1” 12, a schedule 28 b for the child networkdevice “N2” 14, and a schedule 28 c for the child network device “N3”14, where one and only one network device 12 or 14 can transmit duringany given slot time 24.

As illustrated in FIG. 2, the parent network device “N1” 12 allocatesfor itself within the schedule 28 a a transmit timeslot 26 at slot time“HS4” 24 (for unicast transmission “Tx” to the child network device “N2”14), a second transmit timeslot 26 at slot time “HS6” 24 (for unicasttransmission “Tx” to the child network device “N3” 14), and a thirdtransmit timeslot 26 at slot time “H7” 24 (for multicast transmission“Mcast” to all attached child network devices 14). The parent networkdevice “N1” 12 also can allocate within the schedule 28 b for the childnetwork device “N2” 14 a transmit timeslot 26 at slot time “HS1” 24 forunicast transmission (“Tx”) to the parent network device “N1” 12. Theparent network device “N1” 12 also can allocate within the schedule 28 cfor the child network device “N3” 14 a transmit timeslot 26 at slot time“HS2” 24 for unicast transmission (“Tx”) to the parent network device“N1” 12, and a retransmit timeslot “R-Tx(N3)” 30 that enables the childnetwork device “N3” 14 to attempt retransmission “R-Tx” if its initialtransmission (“Tx”) based on the transmit timeslot 26 at slot time “HS2”24 was unsuccessful due to a determined absence of any acknowledgementfrom the parent network device “N1” 12 within the slot time “HS2” 24.

The schedule 28 a also identifies that the parent network device “N1” 12is to receive (“Rx”) a data packet at slot times “HS1”, “HS2”, “HS3”,and “HS5”. The schedule 28 b identifies that the child network device“N2” 14 is to receive a data packet from the parent network device “N1”12 at slot times “HS4” and “HS7”. The schedule 28 c identifies that thechild network device “N3” 14 is to receive a data packet from the parentnetwork device “N1” 12 at slot times “HS6” and “HS7” 24.

According to an example embodiment, the parent network device “N1” 12also can allocate one or more peer retransmit timeslots 32 that enable achild network device 14 (e.g., “N3”) to retransmit a data packet onbehalf of another child network device 14 (e.g., “N2”) to the parentnetwork device “N1” 12 if the initial transmission by the other childnetwork device 14 (e.g., “N2”) was unsuccessful. In particular, thechild network device “N3” 14 may be able to promiscuously detecttransmission of a data packet by the child network device “N2” 14 atslot time “HS1” 24, for example due to better wireless transmission orreception characteristics between the child network devices “N2” and“N3” 14 than between the child network device “N2” 14 and the parentnetwork device “N1” 12. The parent network device “N1” 12 can determinethat the child network device “N3” 14 has a greater probability ofsuccessful retransmission on behalf of the child network device “N2” 14,than the child network device “N2” 14 attempting to retransmit its owndata packet that failed to generate an acknowledgement at slot time“HS1” 24 (e.g., due to a retransmit capabilities message from the childnetwork device “N3” 14, described below).

Hence, the parent network device “N1” 12 can allocate within theschedule 28 c the peer retransmit timeslot 32 “R-Tx(N2)” at slot time“HS3” 24, enabling the child network device “N3” 14 to retransmit a datapacket on behalf of the child network device “N2” 14. The parent networkdevice “N1” 12 can unicast timeslot allocation messages 34, illustratedin FIG. 1, that specify the corresponding schedule 28 b allocated forthe child network device “N2” and the corresponding schedule 28 callocated for the child network device “N3”. Hence, the timeslotallocation message 34 received by the child network device “N3” 14specifies the peer retransmit timeslot 32 (at slot time “HS3” 24) thatenables the child network device “N3” 14 to retransmit a data packet onbehalf of the child device “N2” 14 to the parent network device “N1” 12.

As described below, the parent network device “N1” 12 also can allocatea peer retransmit timeslot 32 that enables another child network device(not shown in FIG. 1 or 2) to retransmit the data packet on behalf ofthe child network device “N2” 14 if the child network device “N3” isunable to successfully complete retransmission on behalf of the childnetwork device “N2” using the peer retransmit timeslot 32 at slot time“HS3” 24. The parent network device “N1” 12 also can allocate a parentretransmit timeslot that enables the child network device (e.g., “N3”)14 to retransmit, to the peer child network device “N2” 14, a datapacket on behalf of the parent network device “N1” 12. Hence, the parentnetwork device “N1” 12 can allocate one or more peer retransmittimeslots and/or one or more parent retransmit timeslots that enable achild network device to retransmit data traffic to or from a peer childnetwork device, enabling the child network device to add spatialdiversity as an additional transmission source between the parentnetwork device and the peer child network device.

FIG. 3 illustrates an example implementation of any one of the networkdevices 12 and/or 14 of FIG. 1, according to an example embodiment. Eachapparatus 12 and/or 14 can include a device interface circuit 40, aprocessor circuit 42, and a memory circuit 44. The device interfacecircuit 40 can include one or more distinct physical layer transceiversfor non-deterministic wireless communications (e.g., WiFi, Wifi-Direct,etc.) with any one of the other network devices 12 and/or 14 within thechannel distribution chunk 18 or any other network device within theDODAG; the device interface circuit 40 also can include an IEEE802.15.4e transceiver for wireless deterministic network communications,for example based on sending and receiving data packets via a wireless6TiSCH link 46 according to 6TiSCH.

The processor circuit 42 can be configured for executing any of theoperations described herein, and the memory circuit 44 can be configuredfor storing any data or data packets as described herein, including forexample a timeslot allocation message 34, any allocated schedules 28,detection reliability metrics, etc.

Any of the disclosed circuits of the network devices 12 and/or 14(including the device interface circuit 40, the processor circuit 42,the memory circuit 44, and their associated components) can beimplemented in multiple forms. Example implementations of the disclosedcircuits include hardware logic that is implemented in a logic arraysuch as a programmable logic array (PLA), a field programmable gatearray (FPGA), or by mask programming of integrated circuits such as anapplication-specific integrated circuit (ASIC). Any of these circuitsalso can be implemented using a software-based executable resource thatis executed by a corresponding internal processor circuit such as amicroprocessor circuit (not shown) and implemented using one or moreintegrated circuits, where execution of executable code stored in aninternal memory circuit (e.g., within the memory circuit 44) causes theintegrated circuit(s) implementing the processor circuit to storeapplication state variables in processor memory, creating an executableapplication resource (e.g., an application instance) that performs theoperations of the circuit as described herein. Hence, use of the term“circuit” in this specification refers to both a hardware-based circuitimplemented using one or more integrated circuits and that includeslogic for performing the described operations, or a software-basedcircuit that includes a processor circuit (implemented using one or moreintegrated circuits), the processor circuit including a reserved portionof processor memory for storage of application state data andapplication variables that are modified by execution of the executablecode by a processor circuit. The memory circuit 44 can be implemented,for example, using a non-volatile memory such as a programmable readonly memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM,etc.

Further, any reference to “outputting a message” or “outputting apacket” (or the like) can be implemented based on creating themessage/packet in the form of a data structure and storing that datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a transmit buffer). Any reference to “outputting amessage” or “outputting a packet” (or the like) also can includeelectrically transmitting (e.g., via wired electric current or wirelesselectric field, as appropriate) the message/packet stored in thenon-transitory tangible memory medium to another network node via acommunications medium (e.g., a wired or wireless link, as appropriate)(optical transmission also can be used, as appropriate). Similarly, anyreference to “receiving a message” or “receiving a packet” (or the like)can be implemented based on the disclosed apparatus detecting theelectrical (or optical) transmission of the message/packet on thecommunications medium, and storing the detected transmission as a datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a receive buffer). Also note that the memory circuit44 can be implemented dynamically by the processor circuit 42, forexample based on memory address assignment and partitioning executed bythe processor circuit 42.

FIG. 4 illustrates an example method of allocating one or moreretransmit timeslots to a child network device on behalf of anothertransmitting device, according to an example embodiment. The operationsdescribed with respect to any of the Figures can be implemented asexecutable code stored on a computer or machine readable non-transitorytangible storage medium (e.g., floppy disk, hard disk, ROM, EEPROM,nonvolatile RAM, CD-ROM, etc.) that are completed based on execution ofthe code by a processor circuit implemented using one or more integratedcircuits; the operations described herein also can be implemented asexecutable logic that is encoded in one or more non-transitory tangiblemedia for execution (e.g., programmable logic arrays or devices, fieldprogrammable gate arrays, programmable array logic, application specificintegrated circuits, etc.). Hence, one or more non-transitory tangiblemedia can be encoded with logic for execution by a machine, and whenexecuted by the machine operable for the operations described herein.

In addition, the operations described with respect to any of the Figurescan be performed in any suitable order, or at least some of theoperations in parallel. Execution of the operations as described hereinis by way of illustration only; as such, the operations do notnecessarily need to be executed by the machine-based hardware componentsas described herein; to the contrary, other machine-based hardwarecomponents can be used to execute the disclosed operations in anyappropriate order, or at least some of the operations in parallel.

Referring to FIG. 4, the processor circuit 42 of the parent networkdevice “N1” 12 can organize with other network devices to establish aDODAG overlying the CDU matrix 16, based on the processor circuit 42 ofthe parent network device “N1” 12 appropriating an unused channeldistribution chunk “H” 18 from the CDU matrix 16 relative to neighboringdevices within a detectable interference domain (the network devices“N2” and “N3” also can appropriate, i.e., acquire or claim, their ownunused channel distribution chunks 18 for their own respective subDAGs,for example “I” and “J” during formation of the DODAG). For example, theprocessor circuit 42 can detect an unused channel distribution chunk 18based on receiving, from the device interface circuit 40, information ordata indicating low energy levels (e.g., Received Signal StrengthIndicator (RSSI), etc.) on identifiable cells 20 (identified by wirelesschannel frequency and slot time) that belong to identifiable channeldistribution chunks 18.

The processor circuit 42 of the parent network device “N1” 12 inoperation 50 can allocate one or more transmit timeslots 26 betweenitself and its next-hop attached child devices 14 from the slotframe 22of the appropriated channel distribution chunk “H” 18, and create theassociated schedules 28 a, 28 b, and 28 c for the parent network device“N1” 12, the child network device “N2” 14, and the child network device“N3” 14, respectively (other schedules may be generated for other childnetwork devices that may be attached to the parent network device “N1”12). The processor circuit 42 of the parent network device “N1” 12 isconfigured for generating the timeslot allocation messages 34 and thedevice interface circuit 40 is configured for outputting the timeslotallocation messages 34 to the respective child network devices “N2” and“N3” 14 (assume with respect to operation 50 that the schedule 28 c inthe timeslot allocation message 34 sent to the child network device “N3”14 does not yet specify the peer retransmit timeslot 32). The deviceinterface circuit 40 of the parent network device “N1” 12 also isconfigured for outputting a retransmit capabilities request message(RCRM), generated by the processor circuit 42 of the parent networkdevice “N1” 12, that requests that each child network device 14 reportits retransmit capabilities to the parent network device “N1” 12.

The device interface circuit 40 of each child network device 14 isconfigured for receiving in operation 52 its corresponding timeslotallocation message 34 and the retransmit capabilities request message(RCRM) via the wireless 6TiSCH link 46 from the parent network device“N1” 12. The processor circuit 42 of each child network device 14 isconfigured for storing its corresponding schedule 28 in its memorycircuit 44 for transmission of data packets to the parent network device“N1” 12 according to the corresponding allocated transmit timeslot 26.

The device interface circuit 40 and the processor circuit 42 of eachchild network device 14 also is configured for promiscuously detectingin operation 52 data packets transmitted by other network devices withinthe appropriated channel distribution chunk “H” 18, based on parsingdata packets addressed to other network devices. For example, the childnetwork device “N3” 14 can promiscuously detect the data packetstransmitted between the parent network device “N1” 12 and the childnetwork device “N2” 14 based on promiscuous detection of the timeslotallocation message 34 specifying the schedule 28 b for the child networkdevice “N2” 14. The child network device “N3” in operation 52 can store(in its memory circuit 44) detection reliability metrics for the othertransmitting network devices (e.g., the parent network device “N1” 12,the child network device “N2” 14, any other child network devices,etc.). Example detection reliability metrics can include RSSI, bit errorrate, jitter, etc. Hence, the detection reliability metrics can quantifythe relative ability of the child network device 14 to detect a datapacket transmission from an identified transmitting network device to adestination network device.

The processor circuit 42 of each child network device 14 is configuredfor generating in operation 54 a retransmit capabilities message (RCM)specifying the detection reliability metrics for retransmit capabilitiesthat are stored in its memory circuit 44. The device interface circuit40 is configured for sending in operation 54 the retransmit capabilitiesmessage to the parent network device “N1” 12, enabling the parentnetwork device “N1” 12 to determine the retransmit capabilities of eachof the child network devices 14.

The device interface circuit 40 of the parent network device “N1” 12 isconfigured for receiving in operation 56 the retransmit capabilitiesmessage from each of the attached child network devices 14, includingthe detection reliability metrics. The processor circuit 42 of theparent network device “N1” 12 is configured for associating theretransmit capabilities message to the retransmit capabilities requestmessage 50 (e.g., for sequence tracking purposes), enabling theprocessor circuit 42 in operation 56 to identify from the detectionreliability metrics that the child network device “N3” 14 can detect adata packet transmission to the parent network device “N1” 12 by thechild network device “N2” 14, and/or that the child network device “N3”14 can detect a data packet transmission to the child network device“N2” 14 by the parent network device “N1” 12.

In response to receiving the detection reliability metrics from thechild network devices “N2” and “N3” 14, for example indicating that thechild network device “N3” has better signal quality and/or receptioncapabilities than the child network device “N2” for data traffic betweenthe child network device “N2” and the parent network device “N1” 12, theprocessor circuit 42 of the parent network device “N1” 12 is configuredfor allocating retransmit timeslots in operation 56 to the schedule 28 c(and possibly removing retransmit timeslots from the 28 b). As describedpreviously with respect to FIG. 2, the processor circuit 42 of theparent network device “N1” 12 is configured for allocating in operation56, within the schedule 28 c, the peer retransmit timeslot 32 “R-Tx(N2)”at slot time “HS3” 24, enabling the child network device “N3” 14 toretransmit a data packet on behalf of the child network device “N2” 14.

The parent network device “N1” 12 in operation 56 can unicast an updatedtimeslot allocation message 34 specifying the transmit timeslot 26including the peer retransmit timeslot 32, illustrated in FIG. 1, thatspecifies the schedule 28 c allocated for the child network device “N3”;alternately, the parent network device “N1” 12 can unicast to the childnetwork device “N3” a special allocation message that specifies only thepeer retransmit timeslot 32 and/or the parent retransmit timeslot.Although not illustrated in FIGS. 1 and 2, the processor circuit 42 ofthe parent network device “N1” 12 also can allocate in operation 56 aparent retransmit timeslot on behalf of the parent network device “N1”12 in the schedule 28 c, enabling the child network device 14 toretransmit a data packet on behalf of the parent network device “N1” 12to the child network device “N2” 14.

If the child network device “N2” was previously allocated a retransmittimeslot 30, the device interface circuit 40 of the parent networkdevice “N1” 12 can output an updated timeslot allocation message 34specifying the schedule 28 b with no retransmit timeslot 30 allocated tothe child network device “N2” 14.

The device interface circuit 40 of the child network device “N3” 14 isconfigured for receiving in operation 58 the peer retransmit timeslot 32and/or the parent retransmit timeslot (e.g., in an updated timeslotallocation message 34 or a special allocation message), causing theprocessor circuit 42 in operation 58 to update the schedule 28 c storedin the memory circuit 44. Hence, the timeslot allocation message 34and/or special allocation message received by the child network device“N3” 14 specifies the peer retransmit timeslot 32 (at slot time “HS3”24) that enables the child network device “N3” 14 to retransmit a datapacket on behalf of the child network device “N2” 14 to the parentnetwork device “N1” 12. Any received parent retransmit timeslot alsoenables the child network device “N3” 14 to retransmit a data packet onbehalf of the parent network device “N1” to the child network device“N2” 14.

The processor circuit 42 of the child network device “N3” 14 isconfigured for promiscuously detecting in operation 58 anyun-acknowledged transmission of data packets, either by the peer childnetwork device “N2” and/or the parent network device “N1”, based ondetermining whether a corresponding acknowledgement is detected withinthe corresponding transmit timeslot 26. For example, the processorcircuit 42 of the child network device “N3” is configured in operation58 for detecting a determined absence of an acknowledgement by theparent network device “N1” 12 to a newly-transmitted data packet fromthe child network device “N2” at timeslot “HS1” 24. In response to thedetermined absence of an acknowledgement at slot time “HS1” 24, theprocessor circuit 42 of the child network device “N3” 14 in operation 60is configured for causing unicast retransmission of thenewly-transmitted data packet using the peer retransmit timeslot“R-Tx(N2)” 32 at slot time “HS3” 24, on behalf of the child networkdevice “N2” 14 to the parent network device “N1” 12.

The child network device “N3” 42 also can cause retransmission of a datapacket on behalf of the parent network device “N1” 12. For example,assume the parent network device “N1” allocates a parent retransmittimeslot “R-Tx(N1)” at a slot time “HS8” 24 (not shown in FIG. 2). Theprocessor circuit 42 of the child network device “N3” is configured inoperation 58 for detecting a determined absence of an acknowledgement bythe child network device “N2” 14 to a second transmitted data packetfrom the parent network device “N1” 12 at timeslot “HS4” 24. In responseto the determined absence of an acknowledgement at slot time “HS4” 24,the processor circuit 42 of the child network device “N3” 14 inoperation 60 is configured for causing unicast retransmission of thesecond transmitted data packet using the parent retransmit timeslot“R-Tx(N1)” at slot time “HS8” 24, on behalf of the parent network device“N1” 12 to the child network device “N2” 14.

Assuming another child network device (e.g. “N4” not shown in FIG. 1) isattached to the parent network device “N1” 12 and has transmitted acorresponding retransmit capabilities message to the parent networkdevice “N1” 12, the parent network device “N1” 12 also can allocate apeer retransmit timeslot 32 (e.g., at slot time “HS9” 24) that enablesthe child network device “N4” in operation 62 to retransmit the datapacket on behalf of the child network device “N2” 14 if the childnetwork device “N3” is unable to successfully complete retransmission onbehalf of the child network device “N2” using the peer retransmittimeslot 32 at slot time “HS3” 24. Hence, the parent network device “N1”12 can allocate one or more peer retransmit timeslots and/or one or moreparent retransmit timeslots that enable multiple child network devicesto attempt multiple attempts to retransmit data traffic to or from apeer child network device, enhancing spatial diversity based on addingtransmission sources for retransmission attempts.

According to example embodiments, reliability (e.g., successfulreception of data traffic) can be enhanced in a wireless deterministicnetwork in a scalable manner, without introducing any interference ordegradation in network performance. Retransmission attempts can bedirected to child network devices demonstrating the highest probabilityof successful transmission, while minimizing retransmission attempts byother child network devices having poor transmission or receptioncapabilities with their parent network device.

While the example embodiments in the present disclosure have beendescribed in connection with what is presently considered to be the bestmode for carrying out the subject matter specified in the appendedclaims, it is to be understood that the example embodiments are onlyillustrative, and are not to restrict the subject matter specified inthe appended claims.

What is claimed is:
 1. A method comprising: appropriating, by a parentnetwork device in a destination oriented directed acyclic graph (DODAG)in a wireless deterministic network, a channel distribution chunk as asubset of available cells from a channel distribution/usage (CDU)matrix, each cell representing a corresponding wireless frequencychannel at a corresponding timeslot, the channel distribution chunkenabling the parent network device to establish a sub-directed acyclicgraph, within the DODAG, for communications within the sub-directedacyclic graph without introducing interference to other network devicesoutside of the sub-directed acyclic graph and within an overlappingwireless transmission area in the DODAG; receiving, by the parentnetwork device, a retransmit capabilities message from a first childdevice attached to the parent network device and within the sub-directedacyclic graph, the retransmit capabilities message indicating relativeability of the first child device to detect a data packet transmissionto the parent network device by a second child device within thesub-directed acyclic graph based on stored network reliability metricsfor the second child device, the second child device attached to theparent network device and the second child device a peer of the firstchild device; and allocating in response to receiving the retransmitcapabilities message, by the parent network device, a peer retransmittimeslot to the first child device from within the channel distributionchunk appropriated by the parent network device, the peer retransmittimeslot enabling the first child device to respond to a failedtransmission of a data packet, by the second child device to the parentnetwork device following the data packet transmission, by retransmittingthe data packet on behalf of the second child device to the parentnetwork device.
 2. The method of claim 1, further comprising: receiving,by the parent network device, a second retransmit capabilities messagefrom a third child device attached to the parent network device, thesecond retransmit capabilities message specifying that the third childdevice can detect the data packet transmission by the second childdevice; and allocating, by the parent network device, a second peerretransmit timeslot to the third child device from within the channeldistribution chunk, the second peer retransmit timeslot enabling thethird child device to retransmit the data packet on behalf of the secondchild device to the parent network device if the first child devicecannot retransmit the data packet.
 3. The method of claim 1, wherein theallocating further comprises allocating, to the first child device fromwithin the channel distribution chunk, a parent retransmit timeslot thatenables the first child device to retransmit, to the second childdevice, a data packet on behalf of the parent network device.
 4. Themethod of claim 1, further comprising the parent network devicemulticasting a retransmit capabilities request message, the allocatingbased on associating the retransmit capabilities message to theretransmit capabilities request message.
 5. An apparatus comprising: aprocessor circuit configured for appropriating, as a parent networkdevice in a destination oriented directed acyclic graph (DODAG) in awireless deterministic network, a channel distribution chunk as a subsetof available cells from a channel distribution/usage (CDU) matrix, eachcell representing a corresponding wireless frequency channel at acorresponding timeslot, the channel distribution chunk enabling theparent network device to establish a sub-directed acyclic graph, withinthe DODAG, for communications within the sub-directed acyclic graphwithout introducing interference to other network devices outside of thesub-directed acyclic graph and within an overlapping wirelesstransmission area in the DODAG; and a device interface circuitconfigured for receiving a retransmit capabilities message from a firstchild device attached to the apparatus and within the sub-directedacyclic graph, the retransmit capabilities message indicating relativeability of the first child device to detect a data packet transmissionto the apparatus by a second child device within the sub-directedacyclic graph based on stored network reliability metrics for the secondchild device, the second child device attached to the apparatus and thesecond child device a peer of the first child device; the processorcircuit further configured for allocating, in response to receiving theretransmit capabilities message, a peer retransmit timeslot to the firstchild device from within the channel distribution chunk appropriated bythe apparatus, the peer retransmit timeslot enabling the first childdevice to respond to a failed transmission of a data packet, by thesecond child device to the parent network device following the datapacket transmission, by retransmitting the data packet on behalf of thesecond child device to the apparatus.
 6. The apparatus of claim 5,wherein: the device interface circuit is further configured forreceiving a second retransmit capabilities message from a third childdevice attached to the apparatus, the second retransmit capabilitiesmessage specifying that the third child device can detect the datapacket transmission by the second child device; the processor circuitfurther configured for allocating a second peer retransmit timeslot tothe third child device from within the channel distribution chunk, thesecond peer retransmit timeslot enabling the third child device toretransmit the data packet on behalf of the second child device to theparent network device if the first child device cannot retransmit thedata packet.
 7. The apparatus of claim 5, wherein the processor circuitfurther is configured for allocating, to the first child device fromwithin the channel distribution chunk, a parent retransmit timeslot thatenables the first child device to retransmit, to the second childdevice, a data packet on behalf of the parent network device.
 8. Theapparatus of claim 5, wherein the device interface circuit is configuredfor multicasting a retransmit capabilities request message, theprocessor circuit configured for allocating the peer retransmit timeslotbased on associating the retransmit capabilities message to theretransmit capabilities request message.
 9. One or more non-transitorytangible media encoded with logic for execution by a machine and whenexecuted by the machine operable for: appropriating, by a parent networkdevice in a destination oriented directed acyclic graph (DODAG) in awireless deterministic network, a channel distribution chunk as a subsetof available cells from a channel distribution/usage (CDU) matrix, eachcell representing a corresponding wireless frequency channel at acorresponding timeslot, the channel distribution chunk enabling theparent network device to establish a sub-directed acyclic graph, withinthe DODAG, for communications within the sub-directed acyclic graphwithout introducing interference to other network devices outside of thesub-directed acyclic graph and within an overlapping wirelesstransmission area in the DODAG; receiving, by the parent network device,a retransmit capabilities message from a first child device attached tothe parent network device and within the sub-directed acyclic graph, theretransmit capabilities message indicating relative ability of the firstchild device to detect a data packet transmission to the parent networkdevice by a second child device within the sub-directed acyclic graphbased on stored network reliability metrics for the second child device,the second child device attached to the parent network device and thesecond child device a peer of the first child device; and allocating inresponse to receiving the retransmit capabilities message, by the parentnetwork device, a peer retransmit timeslot to the first child devicefrom within the channel distribution chunk appropriated by the parentnetwork device, the peer retransmit timeslot enabling the first childdevice to respond to a failed transmission of a data packet, by thesecond child device to the parent network device following the datapacket transmission, by retransmitting the data packet on behalf of thesecond child device to the parent network device.
 10. A methodcomprising: sending, by a child network device attached to a parentnetwork device in a wireless deterministic network, a retransmitcapabilities message to the parent network device, the retransmitcapabilities message indicating relative ability of the child networkdevice to detect a data packet transmission to the parent network deviceby a second child device based on stored network reliability metrics forthe second child device, the second child device attached to the parentnetwork device and a peer of the child network device, the child networkdevice and the second child device attached to the parent network devicewithin a sub-directed acyclic graph established by the parent networkdevice and that is within a destination oriented directed acyclic graph(DODAG) based on the parent network device having appropriated a channeldistribution chunk as a subset of available cells from a channeldistribution/usage (CDU) matrix, each cell representing a correspondingwireless frequency channel at a corresponding timeslot, the channeldistribution chunk enabling communications within the sub-directedacyclic graph without introducing interference to other network devicesoutside of the sub-directed acyclic graph and within an overlappingwireless transmission area in the DODAG; and receiving, by the childnetwork device from the parent network device, a peer retransmittimeslot allocated to the child network device in response to the parentnetwork device receiving the retransmit capabilities message, the peerretransmit timeslot allocated by the parent network device from withinthe channel distribution chunk appropriated by the parent networkdevice, the peer retransmit timeslot enabling the child network deviceto respond to a failed transmission of a data packet, by the secondchild device to the parent network device following the data packettransmission, by retransmitting the data packet on behalf of the secondchild device to the parent network device.
 11. The method of claim 10,further comprising: detecting, by the child network device, a determinedabsence of an acknowledgement by the parent network device to anewly-transmitted data packet from the second child device; and thechild network device retransmitting the newly-transmitted data packetusing the peer retransmit timeslot, on behalf of the second child deviceto the parent network device, in response to the determined absence ofthe acknowledgement.
 12. The method of claim 10, further comprising:receiving, by the child network device, a parent retransmit timeslotthat enables the child network device to retransmit, to the second childdevice, a data packet on behalf of the parent network device; detecting,by the child network device, a determined absence of an acknowledgementby the second child device to a second transmitted data packet from theparent network device; and the child network device retransmitting thesecond transmitted data packet using the parent retransmit timeslot, onbehalf of the parent network device to the second child device, inresponse to the determined absence of the acknowledgement.
 13. Themethod of claim 10, further comprising: receiving, by the child networkdevice, a retransmit capabilities request message from the parentnetwork device; determining, by the child network device, detectabilityof the data packet transmission to the parent network device by thesecond child device based on promiscuous detection of the data packettransmission on timeslots allocated to the second child device withinthe channel distribution chunk; and generating the retransmitcapabilities message, responsive to the retransmit capabilities requestmessage, based on the promiscuous detection of the data packettransmission.
 14. The method of claim 13, wherein the generatingincludes specifying, within the retransmit capabilities message,detection reliability metrics based on the promiscuous detection of thedata packet transmission.
 15. An apparatus comprising: a processorcircuit configured for generating a retransmit capabilities message fora parent network device in a wireless deterministic network, theapparatus attached as a child network device to the parent networkdevice, the retransmit capabilities message indicating relative abilityof the apparatus to detect a data packet transmission to the parentnetwork device by a second child device based on stored networkreliability metrics for the second child device, the second child deviceattached to the parent network device and a peer of the apparatus, thechild network device and the second child device attached to the parentnetwork device within a sub-directed acyclic graph established by theparent network device and that is within a destination oriented directedacyclic graph (DODAG) based on the parent network device havingappropriated a channel distribution chunk as a subset of available cellsfrom a channel distribution/usage (CDU) matrix, each cell representing acorresponding wireless frequency channel at a corresponding timeslot,the channel distribution chunk enabling communications within thesub-directed acyclic graph without introducing interference to othernetwork devices outside of the sub-directed acyclic graph and within anoverlapping wireless transmission area in the DODAG; and a deviceinterface circuit configured for sending the retransmit capabilitiesmessage to the parent network device, the device interface circuitfurther configured for receiving, from the parent network device, a peerretransmit timeslot allocated to the apparatus in response to the parentnetwork device receiving the retransmit capabilities message, the peerretransmit timeslot allocated by the parent network device from withinthe channel distribution chunk appropriated by the parent networkdevice, the peer retransmit timeslot enabling the apparatus to respondto a failed transmission of a data packet, by the second child device tothe parent network device following the data packet transmission, byretransmitting the data packet on behalf of the second child device tothe parent network device.
 16. The apparatus of claim 15, wherein: theprocessor circuit is configured for detecting a determined absence of anacknowledgement by the parent network device to a newly-transmitted datapacket from the second child device; the processor circuit configuredfor causing retransmission of the newly-transmitted data packet usingthe peer retransmit timeslot, on behalf of the second child device tothe parent network device, in response to the determined absence of theacknowledgement.
 17. The apparatus of claim 15, wherein: the deviceinterface circuit is configured for receiving a parent retransmittimeslot that enables the apparatus to retransmit, to the second childdevice, a data packet on behalf of the parent network device; theprocessor circuit configured for detecting a determined absence of anacknowledgement by the second child device to a second transmitted datapacket from the parent network device; the processor circuit furtherconfigured for causing retransmission of the second transmitted datapacket using the parent retransmit timeslot, on behalf of the parentnetwork device to the second child device, in response to the determinedabsence of the acknowledgement.
 18. The apparatus of claim 15, wherein:the device interface circuit is configured for receiving a retransmitcapabilities request message from the parent network device; theprocessor circuit is configured for determining detectability of thedata packet transmission to the parent network device by the secondchild device based on promiscuous detection of the data packettransmission on timeslots allocated to the second child device withinthe channel distribution chunk; and the processor circuit is configuredfor generating the retransmit capabilities message, responsive to theretransmit capabilities request message, based on the promiscuousdetection of the data packet transmission.
 19. The apparatus of claim18, wherein the processor circuit is configured for specifying, withinthe retransmit capabilities message, detection reliability metrics basedon the promiscuous detection of the data packet transmission.
 20. One ormore non-transitory tangible media encoded with logic for execution by amachine and when executed by the machine operable for: sending, by achild network device attached to a parent network device in a wirelessdeterministic network, a retransmit capabilities message to the parentnetwork device, the retransmit capabilities message indicating relativeability of the child network device to detect a data packet transmissionto the parent network device by a second child device based on storednetwork reliability metrics for the second child device, the secondchild device attached to the parent network device and a peer of thechild network device, the child network device and the second childdevice attached to the parent network device within a sub-directedacyclic graph established by the parent network device and that iswithin a destination oriented directed acyclic graph (DODAG) based onthe parent network device having appropriated a channel distributionchunk as a subset of available cells from a channel distribution/usage(CDU) matrix, each cell representing a corresponding wireless frequencychannel at a corresponding timeslot, the channel distribution chunkenabling communications within the sub-directed acyclic graph withoutintroducing interference to other network devices outside of thesub-directed acyclic graph and within an overlapping wirelesstransmission area in the DODAG; and receiving, by the child networkdevice from the parent network device, a peer retransmit timeslotallocated to the child network device in response to the parent networkdevice receiving the retransmit capabilities message, the peerretransmit timeslot allocated by the parent network device from withinthe channel distribution chunk appropriated by the parent networkdevice, the peer retransmit timeslot enabling the child network deviceto respond to a failed transmission of a data packet, by the secondchild device to the parent network device following the data packettransmission, by retransmitting the data packet on behalf of the secondchild device to the parent network device.